Tony Politano

In middle of drive today pass. window stuck in down position and unable to come up. No humming nor clicking from door, nor any power drain (dimming of lights) when pressing. I know first step is to test the switch (it is original switch). There are four wires - red, grey, green, brown going to the switch. Which I can just barely get to under the switch. Which one do I test for voltage when engaged?

I will hold off on what to do next as my fingers are crossed that I just had a failed 31 year old switch here.

MainePorsche

Brown is always ground on the 928. Red is +. Grey and green are the switches + reversing polarity to the motor for up and down. How is the driver's window ? Likely old switch which requires surgery. See this.

http://members.rennlist.com/v1uhoh/windowSW.htm

Add: I am nowhere near Wiring Diagrams so I can't tell what fuse to check if need be. Someone will chime in.

First post.
Welcome to the Tank.

MainePorsche

And Tony...you have the oldest 928 I have ever seen.

Tony Politano

A little fat finger and I have a120 year old car! Since the driver side works, I did rule out the fuse already. Thanks

Landseer

tiny flathead can be used at top and bottom of switch body to depress the springs that retain it to the console and remove it. Rocker will snap out also, and depending on which era of switch happens to be in place, might reveal something similar to points that need to be cleaned. Sometimes the leather or plastic covering on console impedes the motion / contact of the switch due to a little wear beneath the rocker. Just some thoughts.

Debrue

My drivers door window quits every now and then. No noise, battery drain, etc

solution is I open the door, slam it shut and the power window works again

MainePorsche

Wires in the bundle going into the door at the 'stress' point can get damaged. Stress point is at hinge point where wires are in that black tube. Wires tightly packed in there and movement can fray them. Another place that can be a culprit is at the wire attachment point to the motor. Good inspection of either will require a door panel dissection. I included the thread below for the door clips you will undoubtedly have to replace. I like them better than the screw in white ones from Porsche.

https://rennlist.com/forums/928-foru...nel-clips.html

WyattsRide

Try opening your door in different degrees of open, while trying the door switch. If in a certain opening position the window works, then it's probably a broken wire in the harness that makes contact in only that position.

This was happening with mine and I put up with it for a while until I decided to pull the door panel and follow the motor wire, where I found the break rather easily. Fixed that and has been great ever since.

ltoolio

Which will also give you a chance to see if there are other wires in similar state of decay, and will let you fix them before other things on the door go bad...

MainePorsche

Yep.
Speakers, mirror, seat memory, door locking too.

crushingday

That's funny

MainePorsche

In a 1895 928S the question of how many 'horses' you have is very relevant.

Hold On

The toggle type switches also tend to loose contact inside. If you have ever opened one up, you will see a couple small contacts embedded into the plastic switch. The contacts will wear at the contact touch point, until the surrounding plastic bottoms out before the contacts make contact. Also after many years of pressing them, the contacts can also be pushed deeper into the plastic switch and loose the contact. I have had this problem with a couple, usually in just one direction over the years. If you need to replace a window toggle switch, stay away from the cheapy $12. ones. They wear down fast.

Red Power to switch
Brown Ground circuit

Green and Grey power to open and close motor direction, just can`t remember which opens and which closes. If you have a Power Probe, you can feed power to each at switch and see which way window goes.